Taxonomic name: Lymantria dispar (Linnaeus, 1759)
Synonyms: Porthetria dispar
Common names: Asian gypsy moth (English), erdei gyapjaslepke (Hungarian), gubar (Romanian), gypsy moth (English), lagarta peluda (Spanish), limantria (Italian), løVstraesnonne (Danish), maimai-ga (Japanese), mniska vel’kohlava (Slovak), Schwammspinner (German), spongieuse (French)
Organism type: insect Lymantria dispar commonly known as the Asian gypsy moth (AGM), is one of the most destructive pests of shade, fruit and ornamental trees throughout the northern hemisphere. It is also a major pest of hardwood forests. AGM caterpillars cause extensive defoliation, leading to reduced growth or even mortality of the host tree. Their presence can destroy the aesthetic beauty of an area by defoliating and killing the trees and covering the area with their waste products and silk. Scenic areas that were once beautiful have become spotted with dead standing trees where AGM has invaded. Also, urticacious hairs on larvae and egg masses cause allergies in some people. Description
Male AGM are brown with a darker brown pattern on their wings. Females are slightly larger and nearly white, with a few dark markings on their wings. Newly hatched caterpillars are black and hairy, later developing a mottled yellow to gray pattern with tufts of bristle like hairs and two rows of blue then red spots on their back.
Please see PaDIL (Pests and Diseases Image Library) Species Content Page Moths: Gypsy moths for high quality diagnostic and overview images. Occurs in:
natural forests, riparian zones, urban areas Habitat description
AGM are found in most temperate natural and artificial forests. Outbreak generally only occur in stands where primary hosts (e.g., Quercus, Populus, etc) comprise > 20% of the basal area. General impacts
In most areas and in most years, AGM remain at low densities and cause no discernible damage. But occasionally, populations reach high densities and these abundant populations may completely defoliate host trees. Most impacts of AGM are associated with the physiological stress in trees caused by defoliation, especially if it occurs several years in a row or in conjunction with drought. These effects include reduction in tree growth, crown dieback and tree mortality. Tree mortality is usually associated with other insects (wood borers) and pathogenic fungi that attack stressed trees. In extreme situations, nearly 100% tree mortality may occur over large areas. The most important impacts occur in urban/suburban settings. Defoliation and tree mortality may be very serious if impacted trees are valuable shade or street trees in urban settings. Also, during outbreaks caterpillars become so numerous that they become a nuisance to homeowners recreating in their yards. Some people also have allergies to the urticacious hairs on AGM larvae, further compromising their recreational experience. Outbreaks typically last 1 to 5 years. Outbreak populations then decline because of starvation and increased disease. Small mammal predators are considered the most important source of mortality in low density populations and may keep sparse AGM populations in check for several years before the next outbreak occurs. AGM defoliation can reduce tree seed production and root sprouting, resulting in poor regeneration. The natural diversity and species composition of native insects, birds, and other animals may be altered during outbreaks through reductions in shelter, food supplies, and other benefits provided by host trees. Notes
Adult females from Asian strains (west of the Ural mtns.) of AGM are capable of flight but European strains are incapable of flight. North American popuations originated from Europe. Larvae of Asian strains also tend to grow larger. Because of these differences, eradication is usually directed more aggressive during incursions of the Asian strain. (Brackett 1996) Geographical range
Native range: AGM is native to southern Europe, northern Africa, central and southern Asia, and Japan (Martin 2000). The European strain has been introduced to the United States and Canada and is now present in most of northeastern N. America but its range is expanding to the south and west. Introduction pathways to new locations
Ignorant possession: Egg masses of AGM can be transported inadvertently. AGM egg masses are tolerant of extremes in temperature and moisture and travel well on logs, lawn furniture, nursery stock, pallets, shipping containers, and on the hulls and riggings of ships (APHIS, 2003).
Caterpillars attach to travelers and their possessions. They can hitch rides and travel across the continent this way.
Local dispersal methods
Hikers' clothes/boots: Caterpillars attach to travelers and their possessions.
Natural dispersal (local): Late instar larvae may crawl up to 100 m
On animals (local): Newly hatched caterpillars travel to the top of their host tree, where winds can carry them to other trees. Young larvae have hairs with small air pockets that may keep them airborne for miles when the wind is strong. Management information
Preventative measures: Landscapes may be protected from AGM in many different ways. One way is the forest can be altered to prevent outbreaks. High-risk forests can be harvested before outbreaks occur to prevent some economic loss. Thinning stands of medium to high quality can increase the vigor of surviving trees, reducing the risk of major outbreak. Thinning to reduce the proportion of primary AGM hosts can also reduce the frequency and intensity of defoliation. After defoliation has occurred, salvage logging can be carried out within 6 to 12 months of tree death to prevent complete economic loss and to advance regeneration. In New Zealand legislation and quarantine procedures may require vessels from areas with established AGM populations before entering port to undergo 'high risk' inspection for AGM egg masses eight kilometres off shore. If found, the vessel is directed back to the 20 nautical mile limit for cleaning, before 'high risk' inspection will be continues once again at eight kilometres off shore (M. Dijkhuis pers. comm April 2005).
Physical: Mating disruption is commonly used in eradication and barrier zone activities. Other control measures include mass-trapping (for eradication) and manual removal of egg masses by home owners.
Chemical: Aerial spraying of populations is the most common method for eradicating new isolated populations and is also used to supress outbreaks in well established populations. Aerial applications are conducted synthetic insecticides such as diflubenzuron (Dimilin), carbaryl (Sevin), and mimic (tebufenozide).
Biological: The most common eradication method used against AGM is the naturally occurring Bacillus thuringiensis (Bt) bacteria. Bt produces a caterpillar–specific toxin. When sprayed on tree leaves, Bt will disrupt the digestive system of caterpillars that ingest the leaves, suppressing their appetites. The caterpillars' movement then slows, and death results, generally in 7 to 10 days (APHIS, 2003). For more information on Bt please see About Bt . Nutrition
AGM feeds on over 500 varieties of trees and shrubs. They prefer oak, alder broadleaf trees, Douglas fir, and western hemlock needle trees. Reproduction
The female lays egg masses on tree trunks, undersides of limbs, rocks, buildings, vehicles, and other human-made objects. Females produce one egg mass per year around the beginning of May. Each egg mass hatches between 100 and 1,500 tiny caterpillars. Egg masses are ovate in shape, orange-yellow in colour and covered with hairs from the female's body. Lifecycle stages
In European (and N. American strains) Male AGM caterpillars go through five growth stages and females go through six stages. In the fifth and sixth stages, they feed most heavily and on the widest range of vegetation. Males and females of Asian strains may have 6 or 7 larval instars. This species has been nominated as among 100 of the "World's Worst" invaders Reviewed by: Major update under progress
Dr. Andrew Liebhold Northeastern Research Station USDA Forest Service. USA
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
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Last Modified: Friday, 31 March 2006
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